An 11kv system consisting of an underground cable to a sub station about 300 me

An 11kv system consisting of an underground cable to a sub
station about 300 meters away was shut down for about 10
hrs. On energising, it tripped off on earth fault about
10---20 mins later 6 times but since than it is not
tripping.its already 3 weeks now. The SPAJ was found to be
fine. what could be the cause.No test had been done to
determine the cause of the trippings till now because of
demand.

Question Posted / pillay

2 Answers
4650 Views
I also Faced
E-Mail Answers

Answers were Sorted based on User's Feedback

An 11kv system consisting of an underground cable to a sub station about 300 meters away was shut d..

Answer / k.prakashchandra

If only you had replaced the breaker cubicle and test
charged you would have come to conclusion.If the all 3 poles
do not close almost at the same time and there is a time
gap, the breaker is likely to trip on EFR due to the
unbalanced current in case of 2 OCR + 1 EFR protection
scheme.In such cases it is advisable to test charge on no
load during the second time and confirm the mechanical fault
which is not consistent & does not occur always.

Is This Answer Correct ?

1 Yes

0 No

An 11kv system consisting of an underground cable to a sub station about 300 meters away was shut d..

Answer / pillay

thanks but I had managed to ON the system and remained
energized with some load for a few minutes (10 -20 mins)
before it tripped again on earth fault , it happened 6 times
on (4/6/2011) and till today (13/07/2011) no problem. we
are using ABB spaj oc/ef relay.

Is This Answer Correct ?

0 Yes

0 No

Post New Answer

More Electrical Engineering Interview Questions

In DC current-excitation to transformer, why it sucks more current? Eventhough there is no power transfer between primary and secondary? R is very low so it should suck less current only na thn y its current increases?

2 Answers Cairn,

what is principle of DG

5 Answers

what is dielectric heating

1 Answers

star delta starter contorl circuit... drawing..

0 Answers

If mutual flux is 1.2wb & power factor is 0.8 lag , then what is the Useful flux of a transformer?

0 Answers Nalco, NTPC,

placing earthing pit in pathway is correct or wrong??. placing earthing wireGI1/18 inside walls is correct or wrong?. explain!!!

0 Answers

An alternator is started without excitation then how much voltage it will produced at strating at full rpm??

4 Answers

WHAT IS SEMICONDUCTOR? EXPLAIN DETAIL. FOR EXAMPLE TAKE A PENCIL.THE LEAD IS MADE UP OF GRAPHITE IT IS A CONDUCTOR.THE OUTER COVER IS MADE UP OF WOOD IT IS INSULATOR.PENCIL IS A SEMICODUCTOR MATERIAL.

5 Answers

how to select correct size of power cable for inverter duty motor

0 Answers

what is smart&micro grid technology?under coal gassification?

0 Answers

In stepdown transformer 11/415 volt two nos.(R & Y)HT side fuse is blown ,what will be voltage of ry,rb,yb in secondary side

5 Answers NTPC,

what is meant by servo motor ? how its operating either AC or DC?

0 Answers

For more Electrical Engineering Interview Questions Click Here